Biaxially oriented layered polyester film and film with hard coat layer

ABSTRACT

There is provided an easily adhesive, biaxially oriented laminated polyester film for optical use which has excellent adhesion, transparency and easy slipperiness. The biaxially oriented laminated film has a coating layer formed on at least one surface of an aromatic polyester film, the coating layer containing either a polyester resin, an acrylic resin and wax or a polyester resin and an acrylic resin having an oxazoline group and an alkylene oxide chain.

TECHNICAL FIELD

[0001] The present invention relates to a biaxially oriented laminatedfilm and a hard coat laminated film. More specifically, the presentinvention relates to a biaxially oriented laminated film which has acoating layer comprising a specific composition formed on at least onesurface of a polyester film and has excellent adhesion, transparency andeasy slipperiness, and to a hard coat laminated film.

BACKGROUND ART

[0002] A polyester film, particularly a biaxially oriented polyethyleneterephthalate film and a biaxially oriented polyethylene naphthalatefilm are widely used, due to their excellent mechanical properties, heatresistance and chemical resistance, as raw materials for magnetic tapes,ferromagnetic thin film tapes, photographic films, packaging films,films for electronic parts, electrical insulating films, films forlaminating metal plates, films to be stuck on surfaces of glassdisplays, and protective films for a variety of members.

[0003] In recent years, a polyester film is often used for a variety ofoptical applications. For example, it is used as base films for a prismlens sheet, touch screen and backlight which are members for a liquidcrystal display device, a base film for an antireflective film and abase film for an explosion-proof film (used to prevent glass fromscattering upon implosion of CRT) for a display. Base films used forsuch optical applications must have excellent transparency and excellenteasy adhesions to a prism lens, a hard coat layer, an adhesive layer andan antireflection layer.

[0004] The polyester film generally has poor adhesion to a prism lens orhard coat layer comprising a material other than a polyester, e.g., anacrylic resin, as a main component. To improve the poor adhesion, it isproposed to laminate an easily adhesive layer using a polyester resin,an acrylic resin or an urethane resin on surfaces of the polyester film(refer to JP-A 10-119215 and JP-A 2000-246855). However, easily adhesivelayers proposed in these publications may exhibit insufficient adhesionsdepending on applications. For example, the easily adhesive layers havesuch a problem that when a polyester film having the easily adhesivelayers formed thereon is used as a film for CRT, the film exhibitsinsufficient adhesion to an adhesive layer on the other side of the filmwhile exhibiting good adhesion to a hard coat layer.

[0005] Further, a filler (lubricant) is generally introduced into thepolyester film so as to improve slipperiness (easy slipperiness) of thefilm. However, when the polyester film is used as a base material foroptical applications, an amount of filler to be added must be minimizedsince transparency is required. However, when the amount of the fillerto be added is small, the surfaces of the film become flat, so thatthere arises a problem that the surfaces of the film stick to each otherwhen the film is rolled up so as to make the surfaces of the filmcontact with each other and the stuck portions may become surfacedefects of the film when the film is unrolled. Further, sinceslipperiness between the surfaces of the film is poor, the film isdifficult to handle, so that there occurs a problem that scratches areformed on the surfaces of the film during production or processing ofthe film. These problems are particularly noticeable when a resin havinga low glass transition point is used in the easily adhesive layers so asto improve adhesion of the polyester film.

[0006] Meanwhile, in recent years, use of the polyester film as asurface protecting material for window glass, a showcase, glasses, ameter, a display and a lamp has been receiving attention. To be used forsuch a purpose, the polyester film must have excellent surface hardnessand abrasion resistance as well as sufficient transparency andantireflectivity.

[0007] To satisfy such a requirement, it has been attempted to laminatea hard coat (HC) layer and an antireflection (AR) layer on the polyesterfilm. However, due to lack of adhesion to the polyester film, asatisfactory result is not obtained, yet.

[0008] As a method for improving the adhesion of the polyester film, forexample, a method in which an aqueous polyester having a glasstransition point of 40 to 85° C. is coated on a base film of a transferfilm for in-molding so as to improve adhesion to a medium layer is known(refer to JP-A 7-156358).

[0009] However, although the adhesion between the base film in thetransfer film for in-molding and the medium layer is improved by themethod, adhesion in other applications is often not improved to asufficiently satisfactory level.

[0010] Meanwhile, to obtain an easily slippery polyester film havingflat surfaces, it is known to form a coating film comprising acomposition containing a polyurethane or acrylic resin and a fatty acidamide or bisamide on surfaces of a polyester film (refer JP-A63-194948).

[0011] However, the publication does not indicate that adhesion isimproved by use of the fatty acid amide or bisamide.

[0012] Further, it is also known that a laminate having good surfacehardness and abrasion resistance is obtained by forming a polyesterresin layer on a polyethylene terephthalate layer and then forming aradiation curable layer having specific composition on the polyesterresin layer (refer to JP-B 7-80281). However, the laminate lacks generalversatility due to use of the special curable layer and is not fullysatisfactory in terms of adhesion.

[0013] In recent years, due to rapid proliferation of personalcomputers, demand for an antiglare (antireflection) transparent boardfor a personal computer display which provides good visibility over along time, displays images with high hue contrasts, causes littleexhaustion on an operator and is not easily scratched when wiped to becleaned has been increasing, and improvements of the above technologiesare desired.

DISCLOSURE OF THE INVENTION

[0014] It is an object of the present invention to provide a laminatedfilm which is free from the problems of the prior art and has excellentadhesions to functional layers to be used in a variety of opticalapplications as well as excellent transparency and easy slipperiness.

[0015] It is another object of the present invention to provide a hardcoat laminated film which is free from the problems of the prior art,displays images with high hue contrasts, has excellent adhesion, goodsurface hardness and, in particular, cracking resistance and sufficienttransparency and antireflectivity and is suitable particularly for asurface layer of a CRT display for a personal computer.

[0016] Other objects and advantages of the present invention will beapparent from the following description.

[0017] According to the present invention, firstly, the above objectsand advantages of the present invention are achieved by a biaxiallyoriented laminated polyester film (hereinafter may also be referred toas “first biaxially oriented laminated film”) comprising:

[0018] (A) an aromatic polyester film, and

[0019] (B) a coating layer containing a polyester resin, an acrylicresin and wax, said coating layer being laminated on at least onesurface of the aromatic polyester film.

[0020] Secondly, the above objects and advantages of the presentinvention are achieved by a biaxially oriented laminated polyester film(hereinafter may also be referred to as “second biaxially orientedlaminated film”) comprising:

[0021] (A) an aromatic polyester film, and

[0022] (B) a coating layer containing a polyester resin and an acrylicresin having an oxazoline group and an alkylene oxide chain, saidcoating layer being laminated on at least one surface of the aromaticpolyester film.

[0023] According to the present invention, thirdly, the above objectsand advantages of the present invention are achieved by a hard coatlaminated film comprising the above biaxially oriented laminatedpolyester film of the present invention and a hard coat layer laminatedon the coating layer (B) of the film, the hard coat layer havinguniversal hardness (UC) which satisfies the following relationalexpression:

0.6×UC≦UHF≦1.2×UC

[0024] wherein UC is the universal hardness of the hard coat layer, andUHF is universal hardness measured from the coating layer (B) side ofthe biaxially oriented laminated polyester film.

PREFERRED EMBODIMENTS OF THE INVENTION

[0025] Hereinafter, the present invention will be described in detail.Firstly, a first biaxially oriented laminated film will be described.

[0026] Aromatic Polyester

[0027] An aromatic polyester constituting an aromatic polyester film inthe present invention is a substantially linear aromatic polyestersynthesized from an aromatic dibasic acid or an ester forming derivativethereof and a diol or an ester forming derivative thereof.

[0028] Specific examples of the aromatic polyester include polyethyleneterephthalate, polyethylene isophthalate, polybutylene terephthalate,poly(1,4-cyclohexylenedimethyleneterephthalate), andpolyethylene-2,6-naphthalene dicarboxylate. The aromatic polyester maybe a copolymer of these polymers or a blend of the polymers and a smallamount of other resins. Of these, polyethylene terephthalate andpolyethylene-2,6-naphthalene dicarboxylate are particularly preferredsince they have balanced physical properties such as mechanicalproperties and optical properties.

[0029] These aromatic polyesters may contain an appropriate filler asrequired. As the filler, those which are conventionally known aslubricants for polyester films can be used. For examples, calciumcarbonate, calcium oxide, aluminum oxide, kaolin, silicon oxide, zincoxide, carbon black, silicon carbide, tin oxide, crosslinked acrylicresin particles, crosslinked polystyrene resin particles, melamine resinparticles, crosslinked silicone resin particles and the like can beused.

[0030] As the filler, particles as described above which have an averageparticle diameter of 0.5 to 5 μm are preferably contained in an amountof 0.0001 to 0.1% by weight based on the aromatic polyester. When a filmwith higher transparency is desired, it is preferred to avoid inclusionof the filler. Further, a colorant, an antistatic agent, an antioxidant,an organic lubricant, a catalyst and the like can also be added to thepolyester as required.

[0031] Aromatic Polyester Film

[0032] An aromatic polyester film (A) in the present invention can beobtained by melt-extruding, for example, the above aromatic polyesterinto a film, cooling and solidifying the extrudate on a casting drum toobtain an unstretched film, stretching the unstretched film at atemperature of Tg to (Tg+60)° C. in a longitudinal direction once ormore to a total stretch ratio of 3 to 6 times, stretching thelongitudinally stretched film at a temperature of Tg to (Tg+60)° C. in atransverse direction to a stretch ratio of 3 to 5 times, heat-treatingthe biaxially stretched film at 180 to 230° C. for 1 to 60 seconds asrequired, and reheat-treating the film at a temperature lower than theheat treatment temperature by 10 to 20° C. while allowing the film toshrink 0 to 20% in the transverse direction.

[0033] The aromatic polyester film (A) preferably has a thickness of 25to 300 μm. The upper and lower limits of the film thickness are morepreferably 250 μm and 50 μm, respectively. When the film thickness is inthe above range, the film exhibits favorable strength when used as ahard coat or a substrate for a touch screen, antiglare treatment or thelike.

[0034] Polyester Resin in Coating Layer (B)

[0035] In the present invention, a polyester resin is used as acomponent which constitutes a coating layer (B). As the polyester resin,a polyester resin having a glass transition point of 50 to 100° C. ispreferred. The glass transition point (Tg) is more preferably not higherthan 90° C., particularly preferably not lower than 60° C. Further, thepolyester resin is preferably a polyester which is soluble ordispersible in water (which may contain a small amount of organicsolvents).

[0036] Preferable examples of the polyester resin include polyesterpolymers or copolymers comprising a polybasic acid component and apolyol component such as those shown below. However, components of thepolyester resin are not limited to these monomers.

[0037] Illustrative examples of the above polybasic acid componentinclude terephthalic acid, isophthalic acid, phthalic acid, phthalicanhydride, 2,6-naphthalenedicarboxylic acid, 1,4-cyclohexanedicarboxylicacid, adipic acid, sebacic acid, trimellitic acid, pyromellitic acid,dimer acid, and 5-sodium sulfoisophthalic acid. It is preferred to forma copolyester by use of two or more of these acid components. Further,an unsaturated polybasic acid component such as maleic acid, itaconicacid and a hydroxycarboxylic acid such as p-hydroxybenzoic acid can beused in a very small amount of, for example, not larger than 5 mol %based on all dicarboxylic acid components.

[0038] Illustrative examples of the polyol component include ethyleneglycol, 1,4-butanediol, diethylene glycol, dipropylene glycol,1,6-hexanediol, 1,4-cyclohexanedimethanol, xylene glycol,dimethylolpropane, poly(ethyleneoxide)glycol andpoly(tetramethyleneoxide)glycol.

[0039] Acrylic Resin in Coating Layer (B)

[0040] In the present invention, an acrylic resin is also used asanother component which constitutes the coating layer (B). As theacrylic resin, one having a glass transition point (Tg) of −50 to +50°C. is preferably used. The glass transition point (Tg) of the acrylicresin is preferably not higher than 25° C. The acrylic resin ispreferably one which is soluble or dispersible in water (which maycontain a small amount of organic solvents).

[0041] The acrylic resin can be obtained by polymerizing, preferablycopolymerizing, one or more of the following acryl monomers. However,components of the acrylic resin are not limited to these monomers.

[0042] Illustrative examples of the acryl monomers include alkylacrylate and alkyl methacrylate (wherein the alkyl group is a methylgroup, ethyl group, n-propyl group, isopropyl group, n-butyl group,isobutyl group, t-butyl group, 2-ethylhexyl group, cyclohexyl group orthe like); hydroxy-containing monomers such as 2-hydroxyethyl acrylate,2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate and2-hydroxypropyl methacrylate; epoxy-group-containing monomers such asglycidyl acrylate, glycidyl methacrylate and allyl glycidyl ether;monomers containing a carboxy group or a salt thereof such as acrylicacid, methacrylic acid, itaconic acid, maleic acid, fumaric acid,crotonic acid, styrenesulfonic acid and salts thereof (such as a sodiumsalt, potassium salt, ammonium salt and tertiary amine salt);amido-group-containing monomers such as acrylamide, methacrylamide,N-alkylacrylamide, N-alkylmethacrylamide, N,N-dialkylacrylamide,N,N-dialkyl methacrylate (wherein the alkyl group is a methyl group,ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutylgroup, t-butyl group, 2-ethylhexyl group, cyclohexyl group or the like),N-alkoxyacrylamide, N-alkoxymethacrylamide, N,N-dialkoxyacrylamide,N,N-dialkoxymethacrylamide (wherein the alkoxy group is a methoxy group,ethoxy group, butoxy group, isobutoxy group or the like), acryloylmorpholine, N-methylolacrylamide, N-methylolmethacrylamide,N-phenylacrylamide and N-phenylmethacrylamide;oxazoline-group-containing monomers such as 2-vinyl-2-oxazoline,2-vinyl-4-methyl-2-oxazoline, 2-vinyl-5-methyl-2-oxazoline,2-isopropenyl-2-oxazoline, 2-isopropenyl-4-methyl-2-oxazoline and2-isopropenyl-5-methyl-2-oxazoline; and monomers having a polyalkyleneoxide chain resulting from addition of a polyalkylene oxide to acarboxyl group in acrylic acid or methacrylic acid.

[0043] Further, as copolymerizable components, acid anhydride monomerssuch as maleic anhydride and itaconic anhydride; and monomers such asvinyl isocyanate, allyl isocyanate, styrene, α-methylstyrene, vinylmethyl ether, vinyl ethyl ether, vinyl trialkoxysilane, alkylmaleic acidmonoester, alkylfumaric acid monoester, alkylitaconic acid monoester,acrylonitrile, methacrylonitrile, vinylidene chloride, ethylene,propylene, vinyl chloride, vinyl acetate and butadiene can be used.

[0044] Wax in Coating Layer (B)

[0045] Illustrative examples of wax to be used as a component in thecoating layer (B) in the present invention include vegetable waxes suchas a carnauba wax, candelilla wax, rice wax, Japan wax, jojoba oil, palmwax, rosin-modified wax, ouricury wax, sugarcane wax, esparto wax andbark wax; animal waxes such as a beeswax, lanolin, spermaceti wax,Chinese wax and shellac wax; mineral waxes such as a montan wax,ozokerite and ceresin wax; petroleum waxes such as a paraffin wax,microcrystalline wax and petrolatum; and synthetic hydrocarbon waxessuch as a Fischer-Tropsch wax, polyethylene wax, polyethylene oxide wax,polypropylene wax and polypropylene oxide wax.

[0046] Of these waxes, the carnauba wax, paraffin wax and polyethylenewax are particularly preferred since they have good easy adhesions to ahard coat layer and an adhesive layer and impart good slipperiness tothe laminated film. Further, from the viewpoints of environmentalproblems and ease of handling, aqueous dispersions thereof are morepreferable.

[0047] Coating Layer (B)

[0048] The polyester resin which constitutes the coating layer (B), thepolyester resin being preferably a polyester resin having a glasstransition point (Tg) of 50 to 100° C., is preferably contained in thecoating layer in an amount of 50 to 95 wt %. The amount of the polyesterresin in the coating layer is more preferably not larger than 90 wt %,much more preferably not smaller than 60 wt %. Meanwhile, the acrylicresin which constitutes the coating layer (B), the acrylic resin beingpreferably an acrylic resin having a glass transition point (Tg) of −50to +50° C, is preferably contained in the coating layer in an amount of5 to 30 wt %. The amount of the acrylic resin in the coating layer ismore preferably not larger than 25 wt %, much more preferably notsmaller than 10 wt %. When the amount of the polyester resin in thecoating layer exceeds 95 wt % or the amount of the acrylic resin in thecoating layer becomes smaller than 5 wt %, adhesion of the coating layermay become insufficient. When the amount of the acrylic resin exceeds 30wt %, the acrylic resin becomes incompatible with the polyester resin,whereby transparency of the coating layer may deteriorate.

[0049] Further, a content of the wax in the coating layer (B) ispreferably not larger than 20 wt %, particularly preferably 0.5 to 20 wt%. The content of the wax is more preferably 1 to 10 wt %. When thecontent is smaller than 0.5 wt %, slipperiness on the surfaces of thefilm may not be achieved easily. Meanwhile, when the content is largerthan 20 wt %, adhesion of the coating layer to the polyester substrateand/or easy adhesions of the coating layer to the hard coat layer andthe adhesive layer may become insufficient.

[0050] Further, the coating layer may also contain, as its constituents,other components in an amount of not larger than 20 wt %. Illustrativeexamples of the other components include resins other than a polyesterresin and an acrylic resin, a crosslinking agent, e.g., melamine, epoxyand aziridine, an antistatic agent, a colorant, a surfactant, anultraviolet absorber and inert particles (filler).

[0051] Specific examples of the filler include inorganic fine particlessuch as calcium carbonate, magnesium carbonate, calcium oxide, zincoxide, magnesium oxide, silicon oxide, sodium silicate, aluminumhydroxide, iron oxide, zirconium oxide, barium sulfate, titanium oxide,tin oxide, antimony trioxide, carbon black and molybdenum disulfide; andorganic fine particles such as an acrylic crosslinked polymer, a styrenecrosslinked polymer, a crosslinked silicone resin, a fluorocarbon resin,a benzoguanamine resin, a phenol resin and a nylon resin.

[0052] If too big, these fillers fall out of the coating layer, so thatthey preferably have an average particle diameter of not larger than 0.5μm. Meanwhile, if too small, these fillers fail to exhibit slipperiness,so that they preferably have an average particle diameter of 0.005 to0.5 μm, more preferably 0.01 to 0.1 μm. Of these, to prevent awater-insoluble solid substance from precipitating in an aqueousdispersion, a filler having a specific gravity of not larger than 3 ispreferably selected.

[0053] The filler is contained in a composition which forms the coatingfilm in an amount of not larger than 10 wt % based on a total weight ofthe polyester resin, the acrylic resin and the wax.

[0054] Particularly, when a relatively large filler having an averageparticle diameter of not smaller than 0.1 μm is used, its amount ispreferably selected from a range of 5 to 10 wt %, while when a fillerhaving an average particle diameter of 0.01 to 0.1 μm is used, itsamount is preferably selected from a range of 8 to 10 wt %.

[0055] Next, a second biaxially oriented laminated film will bedescribed. The second biaxially oriented laminated film has a differentlayer (B) from that of the above first biaxially oriented laminatedfilm.

[0056] The layer (B) of the second biaxially oriented laminated film isa coating layer containing a polyester resin and an acrylic resin havingan oxazoline group and an alkylene oxide chain.

[0057] As the polyester resin, polyester resins which are the same asthose mentioned above with respect to the first biaxially orientedlaminated film are used. Further, as the acrylic resin having anoxazoline group and an alkylene oxide chain, a copolymer of a monomerhaving an oxazoline group and an acryl monomer having an alkylene oxidechain is preferably used.

[0058] Illustrative examples of the monomer having an oxazoline groupinclude 2-vinyl-2-oxazoline, 2-vinyl-4-methyl-2-oxazoline,2-vinyl-5-methyl-2-oxazoline, 2-isopropenyl-2-oxazoline,2-isopropenyl-4-methyl-2-oxazoline and2-isopropenyl-5-methyl-2-oxazoline.

[0059] Meanwhile, illustrative examples of the acrylic resin having analkylene oxide chain include a monomer having a polyalkylene oxide chainresulting from addition of a polyalkylene oxide to a carboxyl group inacrylic acid or methacrylic acid. The above copolymer may be thoseresulting from copolymerization of the acryl monomers (excluding acrylmonomers having an alkylene oxide chain) and copolymerizable componentsmentioned above with respect to the first biaxially oriented laminatedfilm.

[0060] The polyalkylene oxide chain of the monomer having thepolyalkylene oxide chain may be a polymethylene oxide, a polyethyleneoxide, a polypropylene oxide or a polybutylene oxide. The number ofrepeating units in the polyalkylene oxide chain is preferably 3 to 100.

[0061] As the monomer having an oxazoline group,2-isopropenyl-2-oxazoline is industrially easy to obtain and suitable.Use of an acrylic resin having an oxazoline group improves cohesion ofthe coating layer, thereby further enhancing adhesions of the coatinglayer to the hard coat and the adhesive layer. Further, resistance toabrasion against a metal roll in a film production process or a hardcoat processing process can be imparted to the coating layer.

[0062] Further, use of an acrylic resin having a polyalkylene oxidechain can achieve higher compatibility between the polyester resin andacrylic resin in the coating layer as compared with use of an acrylicresin having no polyalkylene oxide chain, thereby improving transparencyof the coating layer. When the number of repeating units in thepolyalkylene oxide chain is smaller than 3, the compatibility betweenpolyester resin and the acrylic resin is so low that the transparency ofthe coating layer is liable to deteriorate. Meanwhile, when the numberof the repeating units is larger than 100, resistance to moisture andheat of the coating layer is liable to deteriorate. Therefore, toimprove adhesions to the hard coat and the like under a hot and humidatmosphere, an acrylic resin having a polyalkylene oxide chaincomprising 3 to 100 repeating units is preferably used.

[0063] The monomer having an oxazoline group is preferably contained inan amount of 5 to 50 mol %, more preferably 10 to 40 mol %, based on allmonomers constituting the acrylic resin. The monomer having apolyalkylene oxide chain is preferably contained in an amount of 0.1 to20 mol %, more preferably 1 to 10 mol %, based on all monomersconstituting the acrylic resin.

[0064] It is to be understood that for other matters which are notmentioned herein with respect to the second biaxially oriented laminatedfilm, corresponding matters which are mentioned with respect to thefirst biaxially oriented laminated film are applied to the secondbiaxially oriented laminated film as they are or after modificationswhich are self-explanatory to those skilled in the art are made to them.

[0065] The coating layer (B) contains the polyester resin and theacrylic resin in amounts of preferably 5.3 to 94.7 wt % and 5.3 to 94.7wt %, more preferably 50 to 90 wt % and 10 to 50 wt %, respectively,based on a total weight of the polyester resin and the acrylic resin.

[0066] When the amount of the polyester resin exceeds 94.7 wt % or theamount of the acrylic resin having an oxazoline group and a polyalkyleneoxide chain becomes smaller than 5.3 wt %, cohesion of the coating layerdeteriorates, so that adhesions of the coating layer to a hard coat andan adhesive may become insufficient. When the amount of the acrylicresin exceeds 94.7 wt %, adhesion of the coating layer to the polyesterfilm deteriorates, so that the adhesions of the coating layer to thehard coat and the adhesive may become insufficient.

[0067] The coating layer (B) may also contain inert particles in anamount of not larger than 20 wt %, preferably inert particles having anaverage particle diameter of 0.005 to 0.5 μm in an amount of 0.01 to 20wt %, based on the total weight of the polyester resin and the acrylicresin.

[0068] Biaxially Oriented Laminated Film

[0069] The first and second biaxially oriented laminated films of thepresent invention preferably have a haze value of not higher than 1%, acenter line average roughness (Ra) on the surface of the coating layerof 0.002 to 0.01 μm and a friction coefficient (ps) on the surface ofthe coating layer of not larger than 0.8.

[0070] Further, the coating layer preferably have no optical defectshaving a vertical interval of not smaller than 0.5 μm and a maximumdiameter of not smaller than 0.5 μm. When the optical defects having avertical interval of not smaller than 0.5 μm and a maximum diameter ofnot smaller than 0.5 μm are present in the coating layer, interferencefringes and missing portions are liable to occur on images on a CRT, anLCD, a PDP and the like, whereby sharpness and visibility of the imagesare liable to deteriorate. It is more preferable that the coating layerbe free from optical defects having a vertical interval of not smallerthan 0.5 μm and a maximum diameter of not smaller than 0.1 μm.

[0071] The first and second biaxially oriented laminated films of thepresent invention with such properties can be obtained by selectingcompositions which satisfy the above properties of the laminates fromthe above compositions and applying a coating solution containing thesecompositions to at least one surface of an aromatic polyester film so asto form a coating film.

[0072] Coating Solution and Coating

[0073] In the present invention, a coating solution to be used to formthe coating layer is preferably used in the form of a water-base coatingsolution such as an aqueous solution, aqueous dispersion or emulsifiedsolution. To form the coating film, components other than theaforementioned components, e.g., an antistatic agent, a colorant, asurfactant, an ultraviolet absorber and the like can also be added asrequired. Particularly, addition of a lubricant can cause improvementsin slipperiness and blocking resistance.

[0074] The water-base coating solution preferably has a solidconcentration of not higher than 20 wt %, more preferably 1 to 10 wt %.When the solid concentration is lower than 1 wt %, coatability of thecoating solution to the polyester film may be insufficient, while whenthe solid concentration is higher than 20 wt %, stability of the coatingsolution and/or an external appearance of the coating solution whenapplied may be degraded.

[0075] The water-base coating solution can be applied to the aromaticpolyester film at any stage. The coating solution is preferably appliedto the aromatic polyester film during its production process, morepreferably before completion of orientation/crystallization.

[0076] The film before completion of crystallization/orientation is anunstretched film, a monoaxially stretched film obtained by stretching anunstretched film in either a longitudinal direction or a transversedirection, a biaxially stretched film which is obtained by stretching anunstretched film in biaxial directions, i.e., longitudinal andtransverse directions, at low stretch ratios and still remainsstretchable after the biaxial stretching (i.e., a biaxially stretchedfilm before re-stretched in a longitudinal or transverse direction atthe end so as to complete orientation/crystallization), or the like.

[0077] In particular, it is preferred to apply a water-base coatingsolution containing the above composition to an unstretched film or amonoaxially stretched film, stretch the film longitudinally and/ortransversely as it is, and heat-set the stretched film.

[0078] When the water-base coating solution is applied to the film, itis preferred to subject the surface of the film to physical treatmentsuch as corona surface treatment, flame treatment or plasma treatment aspretreatment for improving coatability or to use a surfactant which ischemically inert to a composition in combination with the composition.

[0079] The surfactant promotes wettability of the water-base coatingsolution to the polyester film. Illustrative examples of the surfactantinclude anionic surfactants and nonionic surfactants such aspolyoxyethylene alkyl phenyl ether, polyoxyethylene-fatty acid ester,sorbitan fatty acid ester, glycerine fatty acid ester, fatty acidmetallic soap, an alkylsulfate, an alkylsulfonate and analkylsulfosuccinate. The surfactant is preferably contained in thecomposition which forms the coating film in an amount of 1 to 10 wt %.

[0080] The coating solution is preferably applied in such an amount thatthe coating film would have a thickness of 0.02 to 0.3 μm, preferably0.07 to 0.25 μm. When the thickness of the coating film is too small,adhesion may become insufficient, while when the thickness of thecoating film is too large, blocking may occur or the haze value maybecome high.

[0081] To apply the coating solution, any known coating technique can beused. For example, roller coating, gravure coating, roll brushing, spraycoating, air knife coating, impregnation, curtain coating and the likecan be used solely or in combination. The coating film may be formed onone or both surfaces of the film as required.

[0082] Next, the hard coat laminated film of the present invention willbe described.

[0083] The hard coat laminated film of the present invention, asdescribed above, has a hard coat layer laminated on the coating layer(B) of the first or second biaxially oriented laminated polyester filmof the present invention. The hard coat layer has universal hardness(UC) which satisfies the following relational expression:

0.6×UC≦UHF≦1.2×UC

[0084] wherein UC is the universal hardness of the hard coat layer, andUHF is universal hardness measured from the coating layer (B) side ofthe biaxially oriented laminated polyester film.

[0085] The universal hardness is determined by measuring a relationshipbetween pressures and degrees of distortions of a steel ball by means ofa small distortion surface hardness meter and determining a pressure(gr) corresponding to a given degree of distortion.

[0086] When the universal hardness of the surface of the coating layeris lower than 0.6 times that of the hard coat, an antireflection layercoated and formed on the surface of the hard coat layer is liable to becracked, so that the resulting film is not favorable as a film foroptical use. Meanwhile, when the universal hardness of the surface ishigher than 1.2 times that of the hard coat, the hard coat layer isliable to be cracked, so that the resulting film is not favorable as afilm for optical use.

[0087] To achieve such a relationship by adjustment of the universalhardness of the film, a refractive index nz in a thickness direction ofthe film is varied. When a degree of surfacial orientation is increased,nz is decreased and the universal hardness is increased, while when thedegree of surfacial orientation is decreased, nz is increased and theuniversal hardness is decreased.

[0088] As the hard coat layer, a commonly used hard coat layer such as aradiation curable hard coat layer or a silane-based hard coat layer canbe used. Particularly, the radiation curable hard coat layer ispreferred, and above all, an ultraviolet curable hard coat layer ispreferably used.

[0089] Illustrative examples of an ultraviolet curable composition usedfor formation of the hard coat layer include ultraviolet curablecompositions such as an urethane-acrylate composition, an epoxy-acrylatecomposition and a polyester-acrylate composition.

[0090] To laminate the hard coat layer on the coating layer, acomposition to form the hard coat layer is coated on the coating layerand then cured by heating, irradiation of radiation (such as ultravioletradiation) or other means. The thickness of the hard coat layer is notparticularly limited but is generally around 1 to 15 μm.

[0091] On the thus formed hard coat layer, an antireflection layer mayfurther be formed. The antireflection layer is obtained by laminating anumber of layers having different refractive indices alternately, andits constitution is generally well known. For example, one comprising alow-refractive-index layer (SiO₂, 30 nm), a high-refractive-index layer(TiO₂, 30 nm), a low-refractive-index layer (SiO₂, 30 nm), ahigh-refractive-index layer (TiO₂, 100 nm) and a low-refractive-indexlayer (SiO₂, 100 nm); one comprising a high-refractive-index layer (ITO,20 nm), a low-refractive-index layer (AlSiO, 20 nm), ahigh-refractive-index layer (ITO, 88 nm) and a low-refractive-indexlayer (AlSiO, 88 nm); and one comprising a high-refractive-indexconductive layer (ITO, 20 nm), a low-refractive-index layer (SiO₂, 20nm), a high-refractive-index conductive layer (ITO, 93 nm) and alow-refractive-index layer (SiO₂, 93 nm) are known.

[0092] In the present invention, the antireflection layer can be formedoptionally. The antireflection layer is generally laminated on the hardcoat layer by sputtering. Reflection of extraneous light whichinterferes with visibility of a display can be prevented by means of theantireflection layer.

[0093] In addition to those mentioned above, there is an antireflectionlayer which is a single-layer film which mainly prevents reflection ofyellow light. Such an antireflection layer is suitable for preventingreflection of light on an optical lens since violet which is acomplementary color of yellow can be seen, while a multilayerantireflection film is more suitable for preventing reflection of lighton a display.

[0094] The hard coat layer laminated film of the present invention issuitably used in a light transmission layer of a display.

EXAMPLES

[0095] Hereinafter, the present invention will be described in moredetail with reference to Examples. However, the present invention is notlimited to the following Examples. In the Examples and ComparativeExamples, “part” indicates “part by weight”. Further, in the Examplesand Comparative Examples, properties were evaluated in the followingmanners.

[0096] (1) Haze Value

[0097] A haze value of a film was measured by use of a haze meter(NDH-20) manufactured by Nippon Denshoku Industries Co., Ltd. Haze ofthe film was evaluated in accordance with the following criteria.

[0098] ⊚: haze value≦0.5% . . . Haze of the film is very good.

[0099] ◯: 0.5%<haze value≦1.0% . . . Haze of the film is good.

[0100] X: 1.0% <haze value . . . Haze of the film is poor.

[0101] (2) Center Line Average Surface Roughness (Ra)

[0102] In accordance with JIS B0601, a chart was drawn by use of a highprecision surface roughness meter SE-3FAT manufactured by KosakaLaboratory Ltd. with a needle radius of 2 μm, under a load of 30 mg andat a magnification of 200,000 and a cutoff of 0.08 mm, a portion havinga measured length of L in a direction of the center line of the surfaceroughness curve was extracted from the curve, the roughness curve wasexpressed as Y=f(x) with the center line of the extracted portion beingan X axis and a direction of longitudinal magnification being a Y axis,and a value obtained by the following expression was expressed in theunit “mm”. Further, the measurement was made four times with a referencelength of 1.25 mm, and the center line average surface roughness wasexpressed as an average value thereof.

Ra=(1/L)∫₀ ¹ |f(x)|dx

[0103] (3) Slipperiness

[0104] A coefficient of static friction (ps) between a surface having acoating film formed thereon and a polyester film (surface having nocoating film formed thereon) was measured in accordance with ASTMD1894-63 by use of a slipperiness measuring device manufactured by ToyoTester Industries Co., Ltd. Based on the measured static frictioncoefficient (μs), slipperiness of the film was evaluated in accordancewith the following criteria. By use of the following expression, thestatic friction coefficient (μs) was calculated from tensile strength(F) between the coating film formed surface and the polyester film whichwas measured under a load (W) of 1 kg by use of a glass board as athread board.

[0105] μs=F(g)/W(g)

[0106] ⊚: static friction coefficient (μs)≦0.5 . . . Slipperiness isvery good.

[0107] ◯: 0.5<static friction coefficient (ps)≦0.8 . . . Slipperiness isgood.

[0108] X: 0.8<static friction coefficient (μs) . . . Slipperiness ispoor.

[0109] (4) Coefficient of Friction (μs)

[0110] Glass was placed and fixed under two stacked films, the frontsurface of one of the films being in contact with the back surface ofthe other film. The film in a lower position (i.e., film in contact withthe glass plate) out of the stacked films was taken up on a low-speedroller (about 10 cm/min), and a detector was fixed to one end of thefilm in an upper position (i.e., end of the upper film which is oppositeto a direction in which the lower film was taken up) so as to detecttensile strength (F) between the films. A thread placed on the upperfilm during the detection had a back surface having an area of 50 cm²(80 mm×62.5 mm) and made of 80° neoprene rubber and also had a weight(W) of 1.2 kg.

[0111] A static friction coefficient (μs) was calculated by use of thefollowing expression.

μs=F(g)/W(g)

[0112] (5) Adhesion

[0113] (5-1) Adhesion to Hard Coat Layer

[0114] A hard coat layer having a thickness of 10 μm was formed on acoating-film-formed surface of an easily adhesive laminated film and cutin a cross-cut pattern (consisting of 100 grids each of which has a sizeof 1 mm2). A scotch tape (manufactured by Nichiban Co., Ltd.) having awidth of 24 mm was stuck on the hard coat layer and then peeled abruptlyat a peel angle of 180° . Then, the peeled surface was observed andevaluated in accordance with the following criteria.

[0115] 5: Peeled area is smaller than 10% . . . Adhesion is very good.

[0116] 4: Peeled area is 10% to smaller than 20% . . . Adhesion is good.

[0117] 3: Peeled area is 20% to smaller than 30% . . . Adhesion israther good.

[0118] 2: Peeled area is 30% to smaller than 40% . . . Adhesion is poor.

[0119] 1: Peeled area is 40% or larger . . . Adhesion is very poor.

[0120] (5-2) Adhesion to Adhesive (PSA)

[0121] An adhesive (PSA) layer having a thickness of 20 μm was formed ona coating-film-formed surface of an easily adhesive polyester film, andthe film was stuck to float glass such that the adhesive layer was incontact with the float glass. Then, these were left to stand at 23° C.and 65% RH for one day, and then the film was peeled at a peel angle of900. A state of the adhesive (PSA) remaining on the surface of the glasswas observed and evaluated in accordance with the following criteria.

[0122] As the adhesive (PSA: Pressure Sensitive Adhesive), anurethane-containing acrylate copolymer (wherein the acryl componentcomprised n-butyl acrylate (86 mol %) and methyl acrylate (14 mol %))was used.

[0123] 5: Adhesive (PSA) remaining area is smaller than 10% . . .Adhesion is very good.

[0124] 4: Adhesive (PSA) remaining area is 10% to smaller than 20% . . .Adhesion is good.

[0125] 3: Adhesive (PSA) remaining area is 20% to smaller than 30% . . .Adhesion is rather good.

[0126] 2: Adhesive (PSA) remaining area is 30% to smaller than 40% . . .Adhesion is poor.

[0127] 1: Adhesive (PSA) remaining area is 40% or larger . . . Adhesionis very poor.

[0128] (6) Adhesive Strength

[0129] (6-1) Adhesive Strength to Hard Coat Layer

[0130] A hard coat layer having a thickness of 5 μm was formed on acoating-film-formed surface of an easily adhesive laminated film and cutin a cross-cut pattern (consisting of 100 grids each of which has a sizeof 1 mm2). A scotch tape (manufactured by Nichiban Co., Ltd.) having awidth of 24 mm was stuck on the hard coat layer and then peeled abruptlyat a peel angle of 180° . Then, the peeled surface was observed andevaluated in accordance with the following criteria.

[0131] ⊚: Peeled area is smaller than 10% . . . Adhesive strength isvery good.

[0132] ◯: Peeled area is 10% to smaller than 30% . . . . Adhesivestrength is good.

[0133] X: Peeled area is 30% or larger. . . . Adhesive strength is verypoor.

[0134] (6-2) Adhesive Strength to Adhesive (PSA)

[0135] An adhesive (PSA) layer having a thickness of 10 μm was coated ona coating-film-formed surface of an easily adhesive polyester film.Then, the resulting film was left to stand in a thermo-hygrostat at 60°C. and 80% RH for 24 hours, and then an epoxy-resin-based adhesive wasapplied thereon and then peeled. The results were evaluated inaccordance with the following criteria.

[0136] As the adhesive (PSA: Pressure Sensitive Adhesive), anurethane-containing acrylate copolymer (wherein the acryl componentcomprised n-butyl acrylate (86 mol %) and methyl acrylate (14 molt)) wasused.

[0137] ⊚: Adhesive strength is strong to the extent that base film isruptured.

[0138] ◯: Adhesive is peeled off but film is still practical.

[0139] X: Adhesive is easily peeled off and film is not practical.

[0140] (7) Blocking Resistance

[0141] Two films were stacked such that a coating-film-formed surface ofone of the films made contact with a surface of the other film which hadno coating film formed thereon. To the stacked films, a pressure of 0.6kg/cm² was applied at 60° C. and 80% RH for 17 hours. Thereafter, thefilms were peeled away from each other, and based on the peelingstrength, blocking resistance was evaluated in accordance with thefollowing criteria.

[0142] ⊚: peeling strength<98 mN/5 cm . . . Blocking resistance is verygood.

[0143] ◯: 98 mN/5 cm≦peeling strength<147 mN/5 cm . . . Blockingresistance is good.

[0144] Δ: 147 mN/5 cm≦peeling strength <196 mN/5 cm . . . Blockingresistance is rather good.

[0145] X: 196 mN/5 cm≦peeling strength . . . Blocking resistance ispoor.

[0146] (8) Defects of Coating Layer

[0147] Measurement of Size

[0148] Defects on a coating layer such as crawling, foreign materialsand scratches within an area of 1 m² were examined visually, and whenthey were found, the defects of the coating layer were measured for avertical interval and a size by use of a laser light microscope (VF-750)manufactured by KEYENCE CORPORATION. The number of defects on thecoating layer which had a vertical interval of not smaller than 0.5 μmand a maximum diameter of not smaller than 0.1 μm was counted.

[0149] ⊚: There are no defects on the coating layer which have avertical interval of not smaller than 0.5 μm and a maximum diameter ofnot smaller than 0.1 μm . . . very good

[0150] ◯: There are no defects on the coating layer which have avertical interval of not smaller than 0.5 μm and a maximum diameter ofnot smaller than 0.5 μm. . . . good

[0151] X: There are defects on the coating layer which have a verticalinterval of not smaller than 0.5 μm and a maximum diameter of notsmaller than 0.5 μm . . . poor

[0152] (9) Image Definition and Visibility

[0153] A film was stuck on a CRT (RDF19S) manufactured by MitsubishiElectric Corporation, and occurrences of interference fringes andoptical defects were observed visually.

[0154] ⊚: There are neither interference fringes nor optical defects . .. very good

[0155] ◯: Some interference fringes and optical defects are observed buthave no influences on an image . . . good

[0156] X: Interference fringes and optical defects are observed and haveinfluences on definition and visibility of an image . . . poor

[0157] (10) Abrasion Resistance

[0158] A surface of a hard coat was abraded by use of steel wool #0000so as to check whether the surface of the hard coat was scratched. Ahard coat which was not scratched was evaluated to have good abrasionresistance (◯), and a hard coat which was scratched was evaluated tohave poor abrasion resistance (X).

[0159] (11) Falling Ball Impact Test

[0160] A steel ball having a weight of 0.5 kg was dropped from a heightof 1 m onto a sample placed horizontally on an iron plate three times. Asample having no cracks observed in both an antireflection layer and ahard coat was evaluated as good (◯), and a sample having cracks observedin either or both of an antireflection layer and a hard coat wasevaluated as poor (X).

[0161] (12) Glass Transition Point (Tg)

[0162] Using a differential calorimeter (910 DSC, product of DupontInstruments), 20 mg of a sample filled in an aluminum pan was heatedfrom room temperature to 300° C. at a temperature increasing rate of 20°C./min, kept at 300° C. for 1 minute, then quenched to a temperaturewhich is not higher than room temperature, and re-heated from roomtemperature at temperature increasing rate of 20° C./min so as tomeasure a glass transition point (Tg).

[0163] (13) Thickness of Film

[0164] A thickness of a film having a coating film laminated thereon (orthickness of a film when the sample has no coating film laminatedthereon) was measured at 10 points by means of a micrometer, and anaverage value was calculated from the measurements and taken as thethickness of the film.

[0165] (14) Thickness of Coating Film

[0166] This was calculated from an amount of an applied coating solutionper m² and a solid concentration of the coating solution.

[0167] (15) Glass Transition Temperature

[0168] About 10 mg of sample was filled in an aluminum pan formeasurement, and the pan was mounted on a differential calorimeter(V4.0B2000-type DSC, product of Dupont Instruments). Then, the pan washeated from 25° C. to 300° C. at a rate of 20° C./min, kept at 300° C.for 5 minutes, then taken out of the calorimeter, and immediatelytransferred onto ice so as to be quenched. The pan was mounted on thedifferential calorimeter again and heated from 25° C. at a rate of 20°C./min so as to measure a glass transition temperature (Tg: 0° C.).

[0169] (16) Intrinsic Viscosity

[0170] An intrinsic viscosity (IV:dl/g) of a polyester was measured inan o-chlorophenol solution at 25° C.

Examples 1-1 to 1-3 and Comparative Examples 1-1 to 1-3

[0171] Molten polyethylene terephthalates (intrinsic viscosity=0.65dl/g, glass transition point: 78° C.) were extruded from a die andcooled on a cooling drum in accordance with a conventional method so asto obtain unstretched films. Then, the unstretched films were stretchedto 3.6 times in a longitudinal direction, and aqueous coating solutionswith a solid concentration of 8 wt % of compositions for coating filmsshown in Table 1 were uniformly coated on both surfaces of the stretchedfilms by means of a roll coater. TABLE 1 Composition of Easily AdhesiveLayer (wt %) Coating Polyester Polyester Acrylic Acrylic Inert WettingAgent Resin 1-1 Resin 1-2 Resin 1-1 Resin 1-2 Particles 1-1 Wax 1-1 Wax1-2 Agent 1-1 Coating 70 — 15 — — 5 — 10 Solution 1-1 Coating 67 — 15 —5 — 3 10 Solution 1-2 Coating 67 — 15 — 5 3 — 10 Solution 1-3 Coating —75 15 — — — — 10 Solution 1-4 Coating 75 — — 15 — — — 10 Solution 1-5Coating — 75 — 15 — — — 10 Solution 1-6

[0172] In Table 1, components in the coating layers represent thefollowing polymers and compounds.

[0173] Polyester Resin 1-1: Polyester copolymer containing, as acidcomponents, 70 molt of 2,6-naphthalenedicarboxylic acid, 24 molt ofisophthalic acid and 6 molt of 5-sodium sulfoisophthalic acid and, asglycol components, 90 mol % of ethylene glycol and 10 molt of diethyleneglycol (Tg=85° C).

[0174] The polyester resin 1-1 was produced in the following manner inaccordance with a method described in Example 1 of JP-A 6-116487. Thatis, 188 parts of dimethyl 2,6-naphthalenedicarboxylate, 51 parts ofdimethyl isophthalate, 20 parts of dimethyl 5-sodium sulfoisophthalate,131 parts of ethylene glycol and 10 parts of diethylene glycol werecharged into a reactor, 0.05 parts of tetrabutoxytitanium were addedthereto, and the resulting mixture was heated under a nitrogenatmosphere with a temperature controlled to 230° C. so as to distill outmethanol produced, thereby carrying out an ester interchange reaction.Then, the temperature of the reaction system was gradually increased to255° C. and an internal pressure of the system was reduced to 1 mmHg tocarry out a polycondensation reaction. Thus, the polyester resin 1-1 wasobtained.

[0175] Polyester Resin 1-2: Polyester copolymer containing, as acidcomponents, 40 molt of terephthalic acid, 54 molt of isophthalic acidand 6 molt of 5-sodium sulfoisophthalic acid and, as glycol components,70 molt of ethylene glycol and 30 molt of diethylene glycol (Tg=35° C.).

[0176] To obtain the polyester resin 1-2, a polycondensation reactionwas carried out in the same method as in the case of the polyester resin1-1 except that 92 parts of dimethyl terephthalate, 125 parts ofdimethyl isophthalate, 21 parts of dimethyl 5-sodium sulfoisophthalate,127 parts of ethylene glycol and 36 parts of diethylene glycol werecharged, so as to obtain the polyester copolymer.

[0177] Acrylic Resin 1-1: Acrylic copolymer comprising 15 molt of methylmethacrylate, 75 molt of ethyl acrylate, 5 molt of N-methylolacrylamideand 5 molt of 2-hydroxyethyl methacrylate (Tg=0° C.).

[0178] The acrylic resin 1-1 was produced in the following manner inaccordance with a method described in Production Examples 1 to 3 of JP-A63-37167. That is, 3 parts of sodium lauryl sulfonate as a surfactantand 181 parts of ion exchanged water were charged into a four neck flaskand heated to 60° C. in a current of nitrogen. Then, 0.5 parts ofammonium persulfate and 0.2 parts of sodium hydrogen nitrite were addedthereto as polymerization initiators, and a mixture of 14.9 parts ofmethyl methacrylate, 74.4 parts of ethyl acrylate, 4.3 parts ofN-methylolacrylamide and 6.4 parts of 2-hydroxyethyl methacrylate whichwere monomers was added dropwise over 3 hours while a temperature of thesolution constantly adjusted to 60 to 70° C. Even after completion ofthe dropwise addition, the resulting solution was still kept in theabove temperature range for 2 hours and allowed to continue to reactunder agitation. Then, the resulting solution was cooled, therebyobtaining an aqueous dispersion of the acrylic resin 1-1 with a solidcontent of 35%.

[0179] Acrylic Resin 1-2: Acrylic copolymer comprising 80 mol % ofmethyl methacrylate, 10 molt of ethyl acrylate, 5 molt ofN-methylolacrylamide and 5 molt of 2-hydroxyethyl methacrylate (Tg=80°C.).

[0180] To obtain the acrylic resin 1-2, a polymerization reaction wascarried out in the same manner as in the case of the acrylic resin 1-1except that 79.3 parts of methyl methacrylate, 9.9 parts of ethylacrylate, 4.3 parts of N-methylolacrylamide and 6.4 parts of2-hydroxyethyl methacrylate were charged as monomers, so as to obtain anaqueous dispersion of the acrylic resin.

[0181] Inert Particles 1-1: Silica filler (average particle diameter:100 nm) (product of Nissan Chemical Industries, Ltd., trade name:SNOWTEX ZL)

[0182] Wax 1-1: Carnauba wax (product of Chukyo Yushi Co., Ltd., tradename: SELOSOL 524)

[0183] Wax 1-2: Polyethylene wax (product of Toho Chemical Industry Co.,Ltd., trade name: HITECH E-3100)

[0184] Wetting Agent 1-1: Polyoxyethylene (n=7) lauryl ether (product ofSanyo Chemical Industries, Ltd., trade name: NAROACTY N-70)

[0185] Then, these coated films were dried at 95° C., stretched to 3.8times in a transverse direction at 120° C., shrunk 3% in the widthdirection at 220° C. and heat-set so as to obtain laminated films eachhaving a thickness of 188 μm. The results of evaluations of the obtainedlaminated films are shown in Table 2. The thickness of the coating filmwas 0.15 μm.

Example 1-4

[0186] A molten polyethylene-2,6-naphthalate (intrinsic viscosity =0.60dl/g, glass transition point: 121° C.) was extruded from a die andcooled on a cooling drum in accordance with a conventional method so asto obtain an unstretched film. Then, the unstretched film was stretchedto 3.6 times in a longitudinal direction, and an 8% aqueous coatingsolution of a composition for a coating film (the coating solution 1-1in Table 1) was uniformly coated on both surfaces of the stretched filmby means of a roll coater. Then, the coated film was dried at 105° C.,stretched to 3.8 times in a transverse direction at 140° C., shrunk 3%in the width direction at 230° C. and heat-set so as to obtain alaminated film having a thickness of 188 μm. The results of evaluationsof the obtained laminated film are shown in Table 2. The thickness ofthe coating film was 0.15 μm. TABLE 2 Surface Adhesion Coating Roughness(Ra) Adhesive Blocking Overall Agent Haze (μm) Slipperiness Hard Coat(PSA) Resistance Evaluation Ex. 1-1 Coating ⊚ 0.007 ◯ 5 5 ◯ ◯ Solution1-1 Ex. 1-2 Coating ⊚ 0.007 ⊚ 5 5 ⊚ ⊚ Solution 1-2 Ex. 1-3 Coating ◯0.007 ⊚ 5 4 ⊚ ⊚ Solution 1-3 Ex. 1-4 Coating ⊚ 0.008 ◯ 5 5 ◯ ◯ Solution1-1 C. Ex. 1-1 Coating ⊚ 0.007 X 5 5 X X Solution 1-4 C. Ex. 1-2 Coating⊚ 0.007 X 5 1 Δ X Solution 1-5 C. Ex. 1-3 Coating ⊚ 0.007 X 5 1 X XSolution 1-6

[0187] As is obvious from the results shown in Table 2, the biaxiallyoriented laminated polyester films of the present invention wereexcellent in transparency, slipperiness and adhesions to a hard coatlayer and an adhesive layer as well as blocking resistance and wereuseful as an easily adhesive laminated film for optical use.

[0188] The overall evaluations shown in Table 2 were made based on thefollowing criteria in accordance with the results of evaluations ofhaze, surface roughness, a coefficient of friction, adhesions (to a hardcoat and an adhesive) and blocking resistance.

[0189] ⊚: Most of the properties are very good and none of them are bad. . . overall evaluation is very good.

[0190] ◯: Most of the properties are good and none of them are badoverall evaluation is good.

[0191] X: Some of the properties are bad . . . overall evaluation isbad.

Examples 2-1 to 2-3

[0192] Molten polyethylene terephthalates (intrinsic viscosity=0.64dl/g, glass transition point: 78° C.) were extruded from a die andcooled on a cooling drum in accordance with a conventional method so asto obtain unstretched films. Then, the unstretched films were stretchedto 3.6 times in a longitudinal direction, and aqueous coating solutionswith a solid concentration of 8% of the following compositions forcoating films (shown in Table 3) were uniformly coated on both surfacesof the stretched films by means of a roll coater. TABLE 3 Composition ofEasily Adhesive Layer (wt %) Coating Polyester Acrylic Wax Wax InertParticles Wetting Agent Agent Resin 2-1 Resin 2-1 2-1 2-2 2-1 2-1Coating 60 20 — 10 — 10 Solution 2-1 Coating 67 20 3 — — 10 Solution 2-2Coating 62 20 3 — 5 10 Solution 2-3

[0193] In Table 3, components in the coating layers represent thefollowing polymers and compounds.

[0194] Polyester Resin 2-1: Polyester copolymer containing, as acidcomponents, 90 mol % of terephthalic acid, 4 mol % of isophthalic acidand 6 mol % of 5-sodium sulfoisophthalic acid and, as glycol components,90 mol % of ethylene glycol and 10 mol % of diethylene glycol (Tg=70°C.).

[0195] Acrylic Resin 2-1: Acrylic copolymer comprising 50 mol % ofmethyl methacrylate, 40 mol % of ethyl acrylate, 5 mol % ofN-methylolacrylamide and 5 mol % of 2-hydroxyethyl methacrylate (Tg=40°C.).

[0196] Wax 2-1: Carnauba wax (product of Chukyo Yushi Co., Ltd., tradename: SELOSOL 524)

[0197] Wax 2-2: Paraffin wax (product of Chukyo Yushi Co., Ltd., tradename: SELOSOL 428)

[0198] Inert Particles 2-1: Silica filler (average particle diameter:100 nm) (product of Nissan Chemical Industries, Ltd., trade name:SNOWTEX ZL)

[0199] Wetting Agent 2-1: Polyoxyethylene (n=7) lauryl ether (product ofSanyo Chemical Industries, Ltd., trade name: NAROACTY N-70)

[0200] Then, these coated films were dried at 95° C., stretched to 3.8times in a transverse direction at 120° C., shrunk 3% in the widthdirection at 220° C. and heat-set so as to obtain laminated films eachhaving a thickness of 188 μm. The results of evaluations of the obtainedlaminated films are shown in Table 4. The thickness of the coating filmwas 0.15 μm. Further, the laminated films were prepared in anenvironment whose degree of cleanness belongs to a class of 1,000.

Example 2-4

[0201] A molten polyethylene-2,6-naphthalate (intrinsic viscosity =0.60dl/g, glass transition point: 121° C.) was extruded from a die andcooled on a cooling drum in accordance with a conventional method so asto obtain an unstretched film. Then, the unstretched film was stretchedto 3.6 times in a longitudinal direction, and an aqueous coatingsolution with a solid concentration of 8% of a composition for a coatingfilm (the coating solution 2-1 in Table 3) was uniformly coated on bothsurfaces of the stretched film by means of a roll coater. Then, thecoated film was dried at 105° C., stretched to 3.8 times in a transversedirection at 140° C., shrunk 3% in the width direction at 230° C. andheat-set so as to obtain a laminated film having a thickness of 188 μm.The results of evaluations of the obtained laminated film are shown inTable 4. The thickness of the coating film was 0.15 μm. Further, thelaminated film was prepared in an environment whose degree of cleannessbelongs to a class of 1,000.

Comparative Example 2-1

[0202] A film was obtained in the same process as in Example 2-1 exceptthat no coating layers were formed. The results of evaluations of theobtained film are shown in Table 4.

[0203] As is obvious from the results shown in Table 4, the biaxiallyoriented laminated polyester films of the present invention wereexcellent in image definition, transparency, slipperiness and adhesionsto a hard coat layer and an adhesive layer and were useful as an easilyadhesive laminated film for an antireflective purpose.

[0204] The overall evaluations shown in Table 4 were made based on thefollowing criteria in accordance with the results of evaluations ofdrawbacks (size measurements, image definitions and visibilities),hazes, coefficients of friction and adhesions (to a hard coat and anadhesive) of the coating layers.

[0205] ⊚: Most of the properties are very good and none of them are bad. . . overall evaluation is very good.

[0206] X: Some of the properties are bad . . . overall evaluation isbad. TABLE 4 Drawbacks of Coating Layers Image Adhesion Coating SizeDefinition Adhesive Overall Agent Measurement Visibility HazeSlipperiness Hard Coat (PSA) Evaluation Ex. 2-1 Coating ⊚ ⊚ ⊚ ⊚ 5 4 ⊚Solution 2-1 Ex. 2-2 Coating ⊚ ⊚ ⊚ ⊚ 5 5 ⊚ Solution 2-2 Ex. 2-3 Coating⊚ ⊚ ⊚ ⊚ 5 5 ⊚ Solution 2-3 Ex. 2-4 Coating ⊚ ⊚ ⊚ ⊚ 5 4 ⊚ Solution 2-1 C.Ex. 2-1 None ⊚ ⊚ ⊚ X 1 1 X

Examples 3-1 and 3-2 and Comparative Example 3-1

[0207] Molten polyethylene terephthalates (intrinsic viscosity =0.64dl/g, glass transition point: 78° C.) were extruded from a die andcooled on a cooling drum in accordance with a conventional method so asto obtain unstretched films. Then, the unstretched films were stretchedto 3.6 times in a longitudinal direction, and aqueous coating solutionswith a solid concentration of 8 wt % of the following compositions forcoating films (shown in Table 5) were uniformly coated on both surfacesof the stretched films by means of a roll coater. TABLE 5 Composition ofEasily Adhesive Layer (wt %) Coating Polyester Acrylic Wax Wax WettingAgent Agent Resin 3-1 Resin 3-1 3-1 3-2 3-1 Coating 70 15 5 — 10Solution 3-1 Coating 70 15 — 5 10 Solution 3-2 Coating 74 15 1 — 10Solution 3-3 Coating 60 15 15 — 10 Solution 3-4 Coating 90 — — — 10Solution 3-5

[0208] In Table 5, components in the coating layers represent hefollowing polymers and compounds.

[0209] Polyester Resin 3-1: Polyester copolymer containing, as acidcomponents, 90 mol % of terephthalic acid, 4 mol % of isophthalic acidand 6 mol % of 5-sodium sulfoisophthalic acid and, as glycol components,90 mol % of ethylene glycol and 10 mol % of diethylene glycol (Tg=70°C.).

[0210] Acrylic Resin 3-1: Acrylic copolymer comprising 50 mol % ofmethyl methacrylate, 40 mol % of ethyl acrylate, 5 mol % ofN-methylolacrylamide and 5 mol % of 2-hydroxyethyl methacrylate (Tg=40°C.).

[0211] Wax 3-1: Carnauba wax (product of Chukyo Yushi Co., Ltd., tradename: SELOSOL 524)

[0212] Wax 3-2: Polyethylene wax (product of Toho Chemical Industry Co.,Ltd., trade name: HITECH E-3100)

[0213] Wetting Agent 3-1: Polyoxyethylene (n=7) lauryl ether (product ofSanyo Chemical Industries, Ltd., trade name: NAROACTY N-70)

[0214] Then, these coated films were dried at 95° C., stretched to 3.8times in a transverse direction at 120° C., shrunk 3% in the widthdirection at 220° C. and heat-set so as to obtain laminated films eachhaving a thickness of 188 μm. The results of evaluations of the obtainedlaminated films are shown in Table 6. The thickness of the coating filmwas 0.15 μm.

Example 3-3

[0215] A molten polyethylene-2,6-naphthalate (intrinsic viscosity=0.60dl/g, glass transition point: 121° C.) was extruded from a die andcooled on a cooling drum in accordance with a conventional method so asto obtain an unstretched film. Then, the unstretched film was stretchedto 3.6 times in a longitudinal direction, and an aqueous coatingsolution with a solid concentration of 8% of a composition for a coatingfilm (the coating solution 3-1 in Table 5) was uniformly coated on bothsurfaces of the stretched film by means of a roll coater. Then, thecoated film was dried at 105° C., stretched to 3.8 times in a transversedirection at 140° C., shrunk 3% in the width direction at 230° C. andheat-set so as to obtain a laminated film having a thickness of 188 μm.The results of evaluations of the obtained laminated film are shown inTable 6. The thickness of the coating film was 0.15 μm.

Examples 3-4 and 3-5

[0216] Laminated films were obtained in the same process as in Example3-1 except that the composition for a coating film was changed to thecoating solution 3-3 or 3-4 shown in Table 5. The results of evaluationsof the obtained laminated films are shown in Table 6.

Comparative Example 3-2

[0217] A film was obtained in the same process as in Examples 3-1 to 3-3except that no coating layers were formed. The results of evaluations ofthe obtained film are shown in Table 6. TABLE 6 Surface Adhesion CoatingRoughness (Ra) Adhesive Blocking Overall Agent Haze (μm) SlipperinessHard Coat (PSA) Resistance Evaluation Ex. 3-1 Coating ⊚ 0.006 ⊚ 5 5 ⊚ ⊚Solution 3-1 Ex. 3-2 Coating ⊚ 0.006 ⊚ 5 5 ⊚ ⊚ Solution 3-2 Ex. 3-3Coating ⊚ 0.006 ⊚ 5 5 ⊚ ⊚ Solution 3-1 Ex. 3-4 Coating ⊚ 0.006 ⊚ 5 5 ⊚ ⊚Solution 3-3 Ex. 3-5 Coating ⊚ 0.007 ⊚ 4 4 ⊚ ⊚ Solution 3-4 C. Ex. 3-1Coating ⊚ 0.006 X 5 4 Δ X Solution 3-5 C. Ex. 3-2 None ⊚ 0.006 X 1 1 ⊚ X

[0218] As is obvious from the results shown in Table 6, the biaxiallyoriented laminated polyester films of the present invention wereexcellent in transparency, slipperiness and adhesions to a hard coatlayer and an adhesive layer as well as blocking resistance and wereuseful as an easily adhesive laminated film for optical use.

[0219] The overall evaluations shown in Table 6 were made based on thefollowing criteria in accordance with the results of evaluations ofhaze, surface roughness, a coefficient of friction, adhesions (to a hardcoat and an adhesive) and blocking resistance.

[0220] ⊚: Most of the properties are very good and none of them are bad. . . overall evaluation is very good.

[0221] X: Some of the properties are bad . . . overall evaluation isbad.

Examples 4-1 to 4-4 and Comparative Example 4-1 and 4-2

[0222] Molten polyethylene terephthalates (intrinsic viscosity=0.63dl/g, glass transition point: 79° C.) were extruded from a die andcooled on a cooling drum in accordance with a conventional method so asto obtain unstretched films. Then, the unstretched films were stretchedto 3.4 times in a longitudinal direction, and 8% aqueous coatingsolutions of coating agents (compositions of coating solutions 4-1 to4-6 are compositions for coating films shown in the following Table 7)shown in Table 8 were uniformly coated on both surfaces of the stretchedfilms by means of a roll coater. TABLE 7 Composition of Easily AdhesiveLayer (wt %) Coating Polyester Polyester Acrylic Acrylic Acrylic InertWax Wetting Agent Resin 4-1 Resin 4-2 Resin 4-1 Resin 4-2 Resin 4-3Particles 4-1 4-1 Agent 4-1 Coating 65 — 30 — — — — 5 Solution 4-1Coating — 65 30 — — — — 5 Solution 4-2 Coating 60 — 30 — — 5 — 5Solution 4-3 Coating 55 — 30 — — 5 5 5 Solution 4-4 Coating 65 — — 30 —— — 5 Solution 4-5 Coating 65 — — — 30 — — 5 Solution 4-6

[0223] Polyester Resin 4-1: Acid components comprise 65 molt of2,6-naphthalenedicarboxylic acid, 30 molt of isophthalic acid and 5 moltof 5-sodium sulfoisophthalic acid, and glycol components comprise 90molt of ethylene glycol and 10 molt of diethylene glycol (Tg=80° C.,average molecular weight: 13,000).

[0224] The polyester resin 4-1 was produced in the following method inaccordance with a method described in Example 1 of JP-A 6-116487. Thatis, 44 parts of dimethyl 2,6-naphthalenedicarboxylate, 16 parts ofdimethyl isophthalate, 4 parts of dimethyl 5-sodium sulfoisophthalate,34 parts of ethylene glycol and 2 parts of diethylene glycol werecharged into a reactor, 0.05 parts of tetrabutoxytitanium were addedthereto, and the resulting mixture was heated under a nitrogenatmosphere with a temperature controlled to 230° C. so as to distill outmethanol produced, thereby carrying out an ester interchange reaction.Then, the temperature of the reaction system was gradually increased to255° C. and an internal pressure of the system was reduced to 1 mmHg tocarry out a polycondensation reaction. Thus, the polyester resin 4-1 wasobtained.

[0225] Polyester Resin 5-2: Acid components comprise 60 molt ofterephthalic acid, 35 molt of isophthalic acid and 5 molt of 5-sodiumsulfoisophthalic acid, and glycol components comprise 90 molt ofethylene glycol and 10 molt of diethylene glycol (Tg=45° C., averagemolecular weight: 14,000).

[0226] The polyester resin 4-2 was produced in the following method inaccordance with the method described in Example 1 of JP-A 6-116487. Thatis, 36 parts of dimethyl terephthalate, 21 parts of dimethylisophthalate, 5 parts of dimethyl 5-sodium sulfoisophthalate, 36 partsof ethylene glycol and 2 parts of diethylene glycol were charged into areactor, 0.05 parts of tetrabutoxytitanium were added thereto, and theresulting mixture was heated under a nitrogen atmosphere with atemperature controlled to 230° C. so as to distill out methanolproduced, thereby carrying out an ester interchange reaction. Then, thetemperature of the reaction system was gradually increased to 255° C.and an internal pressure of the system was reduced to 1 mmHg to carryout a polycondensation reaction. Thus, the polyester resin 4-2 wasobtained.

[0227] Acrylic Resin 4-1: This resin comprises 30 molt of methylmethacrylate, 30 molt of 2-isopropenyl-2-oxazoline, 10 molt ofpolyethylene oxide (n=10) methacrylate and 30 molt of acrylamide (Tg=50°C.).

[0228] The acrylic resin 4-1 was produced in the following manner inaccordance with a method described in Production Examples 1 to 3 of JP-A63-37167. That is, 3 parts of sodium lauryl sulfonate as a surfactantand 181 parts of ion exchanged water were charged into a four neck flaskand heated to 60° C. in a current of nitrogen. Then, 0.5 parts ofammonium persulfate and 0.2 parts of sodium hydrogen nitrite were addedthereto as polymerization initiators, and a mixture of 23.3 parts ofmethyl methacrylate, 22.6 parts of 2-isopropenyl-2-oxazoline, 40.7 partsof polyethylene oxide (n=10) methacrylate and 13.3 parts of acrylamidewhich were monomers was added dropwise over 3 hours while a temperatureof the solution constantly adjusted to 60 to 70° C. Even aftercompletion of the dropwise addition, the resulting solution was kept inthe above temperature range for 2 hours and allowed to continue to reactunder agitation. Then, the resulting solution was cooled, therebyobtaining an aqueous dispersion of the acrylic resin 4-1 with a solidcontent of 35%.

[0229] Acrylic Resin 4-2: This resin comprises 30 molt of methylmethacrylate, 40 molt of 2-isopropenyl-2-oxazoline and 30 molt ofacrylamide (Tg=80° C.).

[0230] To obtain the acrylic resin 4-2, polymerization was carried outin the same manner as in the case of the acrylic resin 4-1 except that34.9 parts of methyl methacrylate, 45.2 parts of2-isopropenyl-2-oxazoline and 19.9 parts of acrylamide were charged, soas to obtain an aqueous dispersion of the acrylic resin.

[0231] Acrylic Resin 4-3: This resin comprises 45 mol % of methylmethacrylate, 45 mol % of butyl acrylate, 5 mol % of glycidylmethacrylate and 5 mol % of 2-hydroxyethyl methacrylate (Tg=50° C.).

[0232] To obtain the acrylic resin 4-3, polymerization was carried outin the same manner as in the case of the acrylic resin 5-1 except that38.7 parts of methyl methacrylate, 49.6 parts of butyl acrylate, 6.1parts of glycidyl methacrylate and 5.6 parts of 2-hydroxyethylmethacrylate were charged, so as to obtain an aqueous dispersion of theacrylic resin.

[0233] Inert Particles 4-1: Silica filler (average particle diameter:100 nm) (product of Nissan Chemical Industries, Ltd., trade name:SELOSOL ZL)

[0234] Wax 4-1: Carnauba wax (product of Chukyo Yushi Co., Ltd., tradename: SELOSOL 524)

[0235] Wetting Agent 4-1: Polyoxyethylene (n=7) lauryl ether (product ofSanyo Chemical Industries, Ltd., trade name: NAROACTY N-70)

[0236] Then, these coated films were dried at 95° C., stretched to 3.7times in a transverse direction at 120° C., shrunk 3% in the widthdirection at 220° C. and heat-set so as to obtain easily adhesive filmseach having a thickness of 188 μm. The thickness of the coating film was0.15 μm.

Example 4-5

[0237] A molten polyethylene-2,6-naphthalate (intrinsic viscosity=0.65dl/g, Tg=121° C.) was extruded from a die and cooled on a cooling drumin accordance with a conventional method so as to obtain an unstretchedfilm. Then, the unstretched film was stretched to 3.6 times in alongitudinal direction, and an 8% aqueous coating solution of acomposition for a coating film (the coating solution 4-1 in Table 7) wasuniformly coated on both surfaces of the stretched film by means of aroll coater. Then, the coated film was dried at 105° C., stretched to3.8 times in a transverse direction at 140° C., shrunk 3% in the widthdirection at 230° C. and heat-set so as to obtain an easily adhesivefilm having a thickness of 188 μm. The thickness of the coating film was0.15 μm. TABLE 8 Surface Adhesion Coating Roughness (Ra) AdhesiveBlocking Overall Agent Haze (μm) Slipperiness Hard Coat (PSA) ResistanceEvaluation Ex. 4-1 Coating ⊚ 0.006 ◯ 5 5 ⊚ ◯ Solution 4-1 Ex. 4-2Coating ⊚ 0.006 ◯ 5 5 ⊚ ◯ Solution 4-2 Ex. 4-3 Coating ⊚ 0.007 ⊚ 5 5 ⊚ ⊚Solution 4-3 Ex. 4-4 Coating ⊚ 0.007 ⊚ 5 5 ⊚ ⊚ Solution 4-4 Ex. 4-5Coating ⊚ 0.007 ◯ 5 5 ⊚ ◯ Solution 4-1 C. Ex. 4-1 Coating X 0.010 X 5 2◯ X Solution 4-5 C. Ex. 4-2 Coating X 0.011 X 5 2 ◯ X Solution 4-6

[0238] As is obvious from the results shown in Table 8, the easilyadhesive polyester films for optical use of the present invention wereexcellent in adhesion, transparency and easy slipperiness. The films ofthe present invention are useful for a variety of optical applications,particularly as a base film for a prism lens sheet, a touch panel, abacklight or the like, a base film for an antireflective film and anexplosion-proof base film for a display.

[0239] The overall evaluations shown in Table 8 were made based on thefollowing criteria.

[0240] ⊚: Surface roughness (Ra) is 0.002 to 0.01 μm, adhesion to a hardcoat and adhesion to an adhesive are both 3 or larger, and results ofevaluations of haze, a coefficient of friction and blocking resistanceare all ⊚ (overall evaluation: very good).

[0241] ◯: Surface roughness (Ra) is 0.002 to 0.01 μm, adhesion to a hardcoat and adhesion to an adhesive are both 3 or larger, and some ofresults of evaluations of haze, a coefficient of friction and blockingresistance are ◯ and none of the evaluation results are Δ or X (overallevaluation: good).

[0242] Δ: Surface roughness (Ra) is within 0.002 to 0.01 μm, adhesion toa hard coat and adhesion to an adhesive are both 3 or larger, and someof results of evaluations of haze, a coefficient of friction andblocking resistance are Δ and none of the evaluation results are X(overall evaluation: somewhat good).

[0243] X: Surface roughness (Ra) is out of 0.002 to 0.01 μm, either orboth of adhesion to a hard coat and adhesion to an adhesive are 2 orsmaller or at least one of results of evaluations of haze, a coefficientof friction and blocking resistance are is X (overall evaluation: bad).

Example 5-1

[0244] A molten polyethylene terephthalate (intrinsic viscosity=0.65dl/g, glass transition point: 78° C.) containing 0.007 wt % of poroussilica having an average particle diameter of 1.7 μm was extruded from adie and cooled on a cooling drum in accordance with a conventionalmethod so as to obtain an unstretched film. Then, the unstretched filmwas stretched to 3.2 times in a longitudinal direction, and an 8%aqueous coating solution of a composition for a coating film (thecoating solution 4-4 in Table 7) was uniformly coated on both surfacesof the stretched film by means of a roll coater.

[0245] Then, the coated film was stretched to 3.6 times in a transversedirection at 120° C. while dried at 95° C. and then heat-set at 220° C.so as to obtain an adhesive film for optical use which had a thicknessof 125 μm. The thickness of the coating film was 90 nm, and center linesurface roughness (Ra) of the surface of the coating film was 8 nm. Theresults of evaluations of universal hardness (UHF), haze value,coefficient of friction, adhesion to an adhesive and adhesion to a hardcoat of the surface of the coating film of the obtained film are shownin Table 9.

[0246] Then, on one of the adhesive coating films on the film, anultraviolet curable composition having the following composition wasuniformly coated by use of a roll coater such that the coatedcomposition would have a thickness of 5 μm after cured.

[0247] (Ultraviolet Curable Composition) pentaerythritol acrylate: 45 wt% N-methylolacrylamide: 40 wt % N-vinyl pyrrolidone: 10 wt %1-hydroxycyclohexylphenyl ketone  5 wt %

[0248] Then, the coated composition was exposed to an ultravioletradiation irradiated by a high-pressure mercury-vapor lamp having anintensity of 80 W/cm for 30 seconds so as to be cured, thereby obtaininga hard coat layer. The results of evaluations of abrasion resistance,falling ball impact test, universal hardness (UC) and compatibility withthe following expression (1) of the hard coat layer are shown in Table9.

0.6×UC≦UHF≦1.2×UC  (1)

[0249] On the hard coat layer, a low refractive index layer (SiO₂, 30nm), a high refractive index layer (TiO₂, 30 nm), a low refractive indexlayer (SiO₂, 30 nm), a high refractive index layer (TiO₂, 100 nm) and alow refractive index layer (SiO₂, 100 nm) were formed in this order bysputtering, thereby obtaining a laminate for optical use.

Example 5-2

[0250] A molten polyethylene-2,6-naphthalate (intrinsic viscosity: 0.65dl/g, Tg=121° C.) containing 0.007 wt % of porous silica having anaverage particle diameter of 1.7 μm was extruded from a die and cooledon a cooling drum in accordance with a conventional method so as toobtain an unstretched film. Then, the unstretched film was stretched to3.6 times in a longitudinal direction, and an 8% aqueous coatingsolution of a composition for a coating film (the coating solution 4-4in Table 7) was uniformly coated on both surfaces of the stretched filmby means of a roll coater.

[0251] Then, the coated film was stretched to 3.8 times in a transversedirection at 140° C. while dried at 105° C. and then heat-set at 230° C.so as to obtain an adhesive film for optical use which had a thicknessof 125 μm. The thickness of the coating film was 90 nm, and center linesurface roughness (Ra) of the surface of the coating film was 8 nm. Theresults of evaluations of universal hardness (UHF), haze value,coefficient of friction, adhesion to an adhesive and adhesion to a hardcoat of the surface of the coating film of the obtained film are shownin Table 9.

Example 5-3

[0252] An adhesive film for optical use was obtained in the same processas in Example 5-1 except that a molten polyethyleneterephthalate/isophthalate copolymer (proportion of copolymerizedisophthalic acid component 6 mol %, intrinsic viscosity=0.65 dl/g, glasstransition point=78° C.) containing 0.007 wt % of porous silica havingan average particle diameter of 1.7 μm was extruded from a die andcooled on a cooling drum in accordance with a conventional method so asto obtain an unstretched film. The thickness of the coating film on thefilm was 90 nm, and center line surface roughness (Ra) of the surface ofthe coating film was 8 nm. The results of evaluations of universalhardness (UHF), haze value, coefficient of friction, adhesion to anadhesive and adhesion to a hard coat of the surface of the coating filmof the obtained film are shown in Table 9.

[0253] As is obvious from the results shown in Table 9, the films foroptical use of the present invention were excellent in transparency andadhesion to a hard coat, and laminates for optical use obtained byforming hard coat layers on the films by coating were excellent in crackresistance of the hard coat layers and exhibited good abrasionresistance and antireflectivity. TABLE 9 Universal Hardness Hard CoatLayer Coating UHF UC Expression (1) Coefficient of Adhesion AbrasionFalling Ball Polyester Agent gr gr Compatibility Haze Friction (μs)Adhesive Hard Coat Resistance Impact Test Ex. 5-1 PET Coating 20 20 ◯ ⊚0.35 ◯ ◯ ◯ ◯ Solution 4-4 Ex. 5-2 PEN Coating 23 20 ◯ ⊚ 0.35 ◯ ◯ ◯ ◯Solution 4-4 Ex. 5-3 PET/IA6 Coating 18 20 ◯ ⊚ 0.35 ◯ ◯ ◯ ◯ Solution 4-4

1. A biaxially oriented laminated polyester film comprising: (A) anaromatic polyester film, and (B) a coating layer containing a polyesterresin, an acrylic resin and wax, said coating layer being laminated onat least one surface of the aromatic polyester film.
 2. The film ofclaim 1, wherein the polyester resin has a glass transition temperatureof 50 to 100° C.
 3. The film of claim 1, wherein the acrylic resin has aglass transition temperature of −50 to +50° C.
 4. The film of claim 1,wherein the acrylic resin is soluble or dispersible in water.
 5. Thefilm of claim 1, wherein the acrylic resin has an oxazoline group and analkylene oxide chain.
 6. The film of claim 1, wherein the wax is atleast one wax selected from the group consisting of a carnauba wax, aparaffin wax and a polyethylene wax.
 7. The film of claim 1, wherein thecoating layer (B) contains the polyester resin in an amount of 50 to 95wt %, the acrylic resin in an amount of 5 to 30 wt %, and the wax in anamount of not larger than 20 wt %, based on a total weight of thepolyester resin, acrylic resin and wax.
 8. The film of claim 1, whereinthe coating layer (B) also contains inert particles in an amount of notlarger than 10 wt % based on the total weight of the polyester resin,acrylic resin and wax.
 9. The film of claim 1, wherein a surface of thecoating layer (B) has a center line surface roughness (Ra) of 0.002 to0.01 μm.
 10. The film of claim 1, wherein the surface of the coatinglayer (B) has a coefficient of static friction (ps) of not larger than0.8.
 11. The film of claim 1, wherein the surface of the coating layer(B) has no optical defects having a vertical interval not smaller than0.5 μm and the longest length of not smaller than 0.5 μm.
 12. The filmof claim 1, wherein the aromatic polyester film (A) is a polyethyleneterephthalate film or polyethylene-2,6-naphthalene dicarboxylate. 13.The film of claim 1, which has a haze value of not higher than 1%.
 14. Abiaxially oriented laminated polyester film comprising: (A) an aromaticpolyester film, and (B) a coating layer containing a polyester resin andan acrylic resin having an oxazoline group and an alkylene oxide chain,said coating layer being laminated on at least one surface of thearomatic polyester film.
 15. The film of claim 14, wherein the coatinglayer (B) contains the polyester resin in an amount of 5.3 to 94.7 wt %and the acrylic resin in an amount of 5.3 to 94.7 wt % based on a totalweight of the polyester resin and the acrylic resin.
 16. The film ofclaim 14, wherein the coating layer (B) also contains inert particles inan amount of not larger than 20 wt % based on the total weight of thepolyester resin and the acrylic resin.
 17. The film of claim 14, whereina surface of the coating layer (B) has a center line surface roughness(Ra) of 0.002 to 0.01 μm.
 18. The film of claim 14, which has a hazevalue of not higher than 1%.
 19. The film of claim 1, which is used in alight transmission layer of a display.
 20. The film of claim 14, whichis used in a light transmission layer of a display.
 21. A hard coatlaminated film comprising the biaxially oriented laminated polyesterfilm of claim 1 and a hard coat layer laminated on the coating layer (B)of the film, the hard coat layer having universal hardness (UC) whichsatisfies the following relational expression: 0.6×UC≦UHF≦1.2×UC whereinUC is the universal hardness of the hard coat layer, and UHF isuniversal hardness measured from the coating layer (B) side of thebiaxially oriented laminated polyester film.
 22. The film of claim 21,wherein the hard coat layer comprises a cured resin which is cured aradiation curable resin by irradiation of radiation.
 23. The film ofclaim 21, which is used in a light transmission layer of a display. 24.A hard coat laminated film comprising the biaxially oriented laminatedpolyester film of claim 14 and a hard coat layer laminated on thecoating layer (B) of the film, the hard coat layer having universalhardness (UC) which satisfies the following relational expression:0.6×UC≦UHF≦1.2×UC wherein UC is the universal hardness of the hard coatlayer, and UHF is universal hardness measured from the coating layer (B)side of the biaxially oriented laminated polyester film.
 25. The film ofclaim 24, wherein the hard coat layer comprises a cured resin which iscured a radiation curable resin by irradiation of radiation.
 26. Thefilm of claim 24, which is used in a light transmission layer of adisplay.